Steam methane reforming is the most common and the least expensive method to produce hydrogen at present. Coal can also be reformed to produce hydrogen, through gasification. Hydrogen production by CO2-emitting-free methods are either more expensive compared to those ones using fossil fuel or are in the very early stages of development. Taking into account that United States has more proven coal reserves than any other country coal based technology of hydrogen production is the most attractive. However, effective and low cost carbon sequestration technology has to be developed.
Hydrogen is regarded as the energy for future but to produce and use hydrogen either by direct combustion or in a fuel cell, we need to use other sources of energy. Thus hydrogen or use of any material in producing energy cannot be an environmentally clean and economically viable solution unless we sequester carbon in economically viable way. The use of hydrogen is being promoted on a federal level with massive support from DOE and there is little doubt that we will soon have the hydrogen solution for our transportation and other energy uses. However, it is a sad fact that such energy will continue to be dependent on the use of fossil fuel for long time and may not be economic. To turn things around, we have to use alternate methods of using coal, producing hydrogen and hydrides. Many hydrides are currently under consideration for use in on-board generation of hydrogen and the cost of producing the hydride is an important consideration. This invention is unique because although we use carbon in producing hydrogen, the carbon is sequestered simultaneously as hydrogen is produced and hydrogen is reacted with suitable metals to produce hydrides.
Coal is used extensively in producing synthetic fuels. Use of coal in gasifiers is well established and hydrogen may be produced by the reaction: C+2H2O=CO2+2H2. Gasifiers are operated between 800 and 1500 K, depending on the conditions involving steam, oxygen and/or air a mixture of CO2, CO, H2, CH4 and water. The CO produced can be further processed by the shift-gas reaction to produce H2 with production of CO2: CO+H2O=CO2+H2.
The following is an extract from “The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs (2004), National Academy of Engineering (NAE), Board on Energy and Environmental Systems (BEES)” and shows the importance of the present project:
“Carbon Emissions Associated with Current Hydrogen Production
At the present time, global crude hydrogen production relies almost exclusively on processes that extract hydrogen from fossil fuel feedstock. It is not current practice to capture and store the by-product CO2 that results from the production of hydrogen from these feedstocks. Consequently, more than 100 Mt C/yr are vented to the atmosphere as part of the global production of roughly 38 Mt of hydrogen per year.”
It would then appear that when coal is used in gasifiers or in direct burning in power- and other manufacturing-plants, CO2 and CO are prominent among other gases. Their emission in the atmosphere is not only harming the environment but as considered here is also a waste of resources. For industry this has been an economic issue and someone else's problem. This invention will provide a clear economic incentive to sequester carbon (CO2 and CO) without significantly affecting our current modes of operations. We consider several such processes below.